The boresight between a laser and a return receiving optical system and cameras/detectors is important for alignment of sensors used for large standoff ranges. The ability to accomplish precise alignment verification while on-station enhances the ability to acquire and track (for example) far away targets. However, establishing and maintaining true alignment (in the operational environment) of a typical boresight alignment module can be a very difficult task. In addition, ensuring proper alignment between a boresight module and a transmit/receive sensor unit can also be problematic, resulting in potential alignment errors. A relatively forgiving boresight module that would allow for accurate boresighting is needed.
One known method uses a set of parallel mirrors creating a prism to accomplish boresight alignment. There have been issues with self-alignment and alignment with the transmit/receive sensor unit. Alignment over the entire operational environment is unverified. Moreover, errors have been difficult to trace. Another method uses a lateral transfer hollow retro-reflector (LTHR) and a light source to establish boresighting. This solution uses a light source separate from the laser itself, which introduces undesirable errors and is not as accurate as using the laser itself as a reference. In order to target, track, and range at long standoff ranges the sensors and laser need to be extremely well aligned in object space.